The separate VCL/VCL labels feature can probably help you untangle
your VCL code if it has become too complex. Upgrading from 4.1
to get that feature should be a no-brainer.

The HTTP/2 code is not mature enough for production, and if you
want to start to play with H2, you should not upgrade to 5.0,
but rather track -trunk from github and help us find all the bugs
before the next release.

The Shard director is new in the tree, but it has a lot of live
hours out of tree. Upgrading from 4.1 to 5.0 to get that should
also be a no-brainer.

We have also fixed at lot of minor bugs, and improved many details
here and there, See Upgrading to Varnish 5.0 for more of this.

Until now Varnish Software has done a lot of work for the Varnish
Cache project, but for totally valid reasons, they are scaling that
back and the project either needs to pick up the slack or drop some
of those activities.

It is important that people understand that Free and Open Source
Software isn't the same as gratis software: Somebody has to pay
the developers mortgages and student loans.

A very large part of the Varnish development is funded through the
Varnish Moral License, which enables Poul-Henning Kamp to have
Varnish as his primary job, but right now he is underfunded to the
tune of EUR 2000-3000 per month.

Please consider if your company makes enough money using Varnish
Cache, to spare some money, or employee-hours for its future
maintenance and development.